Energy storage system

ABSTRACT

The present invention relates to an energy storage system. An energy storage system, according to an embodiment of the present invention, relates to an energy storage system for managing power of a system and a direct current (DC) distribution network linked with the system, the energy storage system comprising: a first converter connected between the system and the DC distribution network so as to control a voltage of the DC distribution network; a second converter connected to the DC distribution network; a load connected to the second converter, and controlling the voltage by means of the second converter; a battery connected to the DC distribution network; and a third converter connected between the battery and the load, and controlling discharge of the battery.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a National Stage of International ApplicationNo. PCT/KR2018/013995, filed on Nov. 15, 2018, which claims the benefitof earlier filing date and right of priority to Korean Application No.10-2017-0159941 filed on Nov. 28, 2017, and Korean Application No.10-2017-0159942 filed on Nov. 28, 2017, the contents of which are allhereby incorporated by reference herein in their entirety.

FIELD OF THE INVENTION

The present disclosure relates to an energy storage system that mayefficiently perform charging and discharging of a battery.

BACKGROUND OF THE INVENTION

An energy storage system (ESS) stores generated power in each ofconnected systems including a power plant, a substation, and atransmission line, etc. and selectively and efficiently uses the storedpower when the power is needed, thereby to increase energy efficiency.

The energy storage system may level an electric load having a largefluctuation between time regions and between seasons, thereby improve anoverall load rate. Thus, a power generation cost may be lowered, and aninvestment cost required for expansion of a power facility and anoperation coat thereof may be reduced, thereby lowering an electricityfee, and saving energy.

This energy storage system is installed in a power generation station,transmission and distribution lines, and a customer site in a powersystem. The ESS has functions such as frequency regulation, generatoroutput stabilization using renewable energy, peak shaving, loadleveling, and emergency power supply.

The energy storage system is largely classified into a physical energystorage system and a chemical energy storage system based on an energystorage scheme. The physical energy storage system may employ pumpedstorage power generation, compressed air storage, and flywheel. Thechemical energy storage system may employ a lithium ion battery, a leadacid battery, or a Nas battery.

In this connection, a conventional energy storage system will bedescribed with reference to FIG. 1.

FIG. 1 is a schematic diagram illustrating a conventional energy storagesystem.

In the conventional energy storage system, as shown in FIG. 1, powerdischarged from a battery 180 is supplied to a load 230 via a DC to DCconverter 150.

Accordingly, when the load 230 has an overload which is 1.5 times of anormal load during a discharge operation of the battery 180, the DC toDC converter 150 has the overload of 1.5 times. Further, when the DC toDC converter 150 fails, the power from the battery 180 may not besupplied to the load 230.

BRIEF SUMMARY OF THE INVENTION

A purpose of the present disclosure is to provide an energy storagesystem capable of efficiently performing charging and discharging of abattery.

In order to achieve the purpose, an energy storage system for managingpower of a power system and power of a direct current (DC) powerdistribution network connected to the power system comprises a firstconverter connected to and disposed between the power system and the DCpower distribution network and configured to control voltage of the DCpower distribution network; a second converter connected to the DC powerdistribution network; a load connected to the second converter, whereinthe second converter is configured to control voltage of the load; abattery connected to the DC power distribution network; and a thirdconverter connected to and disposed between the battery and the load,and configured to control discharging of the battery.

Voltage discharged from the battery under control by the third converteris transferred directly to the load.

The energy storage system further comprises a fourth converter connectedto and disposed between the battery and the power system, wherein thefourth converter is configured to control charging and discharging ofthe battery.

Each of the first and fourth converters is configured to convert voltagesupplied from the power system and to charge the battery with theconverted voltage.

Voltage discharged from the battery under control by the third converteris transferred directly to the load, wherein voltage discharged from thebattery under control by the fourth converter is transferred to thepower system.

The energy storage system further comprises: an auxiliary power systemconnected to the load; and a switch configured to selectively connectthe fourth converter to a first node between the power system and thefirst converter or to a second node between the auxiliary power systemand the load.

One end of the switch is connected to the fourth converter, while theother end of the switch is selectively connected to either the firstnode or the second node.

When the power system fails while the fourth converter is connected tothe first node, the fourth converter is connected to the second node viaan switching operation of the switch, the battery is discharged undercontrol by the fourth converter, and voltage discharged from the batteryis transferred to the load via the second node.

The first converter operates in a DC voltage control mode to controlvoltage of the DC power distribution network, wherein the secondconverter operates in a constant voltage constant frequency (CVCF) modeto control voltage of the load, wherein each of the third and fourthconverters operates in a power control mode to control power of thebattery.

The first converter is configured to convert alternating current (AC)voltage supplied from the power system to DC voltage and supply theconverted DC voltage to the DC power distribution network, or to convertDC voltage supplied from the DC power distribution network to AC voltageand supply the converted AC voltage to the power system, wherein thesecond converter is configured to convert DC voltage supplied from theDC power distribution network into AC voltage and supply the convertedAC voltage to the load, wherein the third converter is configured toconvert DC voltage supplied from the battery into AC voltage and supplythe converted AC voltage to the load, wherein the fourth converter isconfigured to convert AC voltage supplied from the power system to DCvoltage and supply the converted DC voltage to the battery, or toconvert DC voltage supplied from the battery to AC voltage and supplythe converted AC voltage to the power system.

In order to achieve the purpose, an energy storage system for managingpower of a power system and power of a direct current (DC) powerdistribution network connected to the power system comprises a firstconverter connected to and disposed between the power system and the DCpower distribution network and configured to control voltage of the DCpower distribution network; a second converter connected to the DC powerdistribution network; a battery connected to the second converter,wherein the second converter is configured to control charging anddischarging of the battery; a third converter connected to the DC powerdistribution network; a load connected to the third converter, whereinthe third converter is configured to control voltage of the load; and afourth converter connected to and disposed between the battery and theload, wherein the fourth converter is configured to control dischargingof the battery.

Voltage discharged from the battery under control by the secondconverter is transferred to the load via the DC power distributionnetwork, wherein voltage discharged from the battery under control bythe fourth converter is transferred directly to the load.

The energy storage system further comprises a fifth converter connectedto and disposed between the battery and the power system, wherein thefifth converter is configured to control charging and discharging of thebattery.

The second converter is configured to convert voltage supplied from theDC power distribution network and to charge the battery with theconverted voltage, wherein the fifth converter is configured to convertvoltage supplied from the power system and to charge the battery withthe converted voltage.

Voltage discharged from the battery under control by the secondconverter is transferred to the load via the DC power distributionnetwork, wherein voltage discharged from the battery under control bythe fourth converter is transferred directly to the load, whereinvoltage discharged from the battery under control by the fifth converteris transferred to the power system.

The energy storage system further comprises: an auxiliary power systemconnected to the load; and a switch configured to selectively connectthe fifth converter to a first node between the power system and thefirst converter or to a second node between the auxiliary power systemand the load.

One end of the switch is connected to the fifth converter, while theother end of the switch is selectively connected to either the firstnode or the second node.

When the power system fails while the fifth converter is connected tothe first node, the fifth converter is connected to the second node viaan switching operation of the switch, the battery is discharged undercontrol by the fifth converter, and voltage discharged from the batteryis transferred to the load via the second node.

The first converter operates in a DC voltage control mode to controlvoltage of the DC power distribution network, wherein each of the secondconverter and the fourth and fifth converters operates in a powercontrol mode to control power of the battery, wherein the thirdconverter operates in a constant voltage constant frequency (CVCF) modeto control voltage of the load.

The first converter is configured to convert alternating current (AC)voltage supplied from the power system to DC voltage and supply theconverted DC voltage to the DC power distribution network, or to convertDC voltage supplied from the DC power distribution network to AC voltageand supply the converted AC voltage to the power system, wherein thesecond converter is configured to convert DC voltage supplied from theDC power distribution network into DC voltage and supply the convertedDC voltage to the battery, or to convert DC voltage supplied from thebattery into DC voltage and supply the converted DC voltage to the DCpower distribution network, wherein the third converter is configured toconvert DC voltage supplied from the DC power distribution network intoAC voltage and supply the converted AC voltage to the load, wherein thefourth converter is configured to convert DC voltage supplied from thebattery into AC voltage and supply the converted AC voltage to the load,wherein the fifth converter is configured to convert AC voltage suppliedfrom the power system to DC voltage and supply the converted DC voltageto the battery, or to convert DC voltage supplied from the battery to ACvoltage and supply the converted AC voltage to the power system.

As described above, according to the present disclosure, efficientlyperforming the charging and discharging of the battery via the variousconverters may allow the overload to be applied to the converter duringthe discharge to be reduced. Furthermore, even when some convertersconnected to the battery fail, a power supply path connecting thebattery and the load to each other may be secured via the remainingconverters. Thus, reliability of the energy storage system may besecured.

In addition to the above-described effects, specific effects of thepresent disclosure will be described in describing specific details forcarrying out the disclosure.

BRIEF DESCRIPTIONS OF DRAWINGS

FIG. 1 is a schematic diagram illustrating a conventional energy storagesystem.

FIG. 2 is a schematic diagram illustrating an energy storage systemaccording to an embodiment of the present disclosure.

FIG. 3 is a schematic diagram illustrating a power flow according tobattery charging and discharging in FIG. 2.

FIG. 4 is a schematic diagram illustrating an energy storage systemaccording to another embodiment of the present disclosure.

FIG. 5 is a schematic diagram illustrating a power flow according tobattery charging and discharging in FIG. 4.

FIG. 6 is a schematic diagram illustrating an energy storage systemaccording to still another embodiment of the present disclosure.

FIG. 7 and FIG. 8 is a schematic diagram illustrating a power flowaccording to battery charging and discharging of FIG. 6.

FIG. 9 is a schematic diagram illustrating an energy storage systemaccording to yet still another embodiment of the present disclosure.

FIG. 10 is a schematic diagram illustrating a power flow according tobattery charging and discharging in FIG. 9.

FIG. 11 is a schematic diagram illustrating an energy storage systemaccording to further yet still another embodiment of the presentdisclosure.

FIG. 12 is a schematic diagram illustrating a power flow according tobattery charging and discharging in FIG. 11.

FIG. 13 is a schematic diagram illustrating an energy storage systemaccording to further yet still another embodiment of the presentdisclosure.

FIG. 14 and FIG. 15 are schematic diagrams illustrating a power flowaccording to battery charging and discharging in FIG. 13.

DETAILED DESCRIPTION OF THE INVENTION

The purposes, features and advantages as above-described will bedescribed in detail below with reference to the accompanying drawings.Accordingly, a person with ordinary skill in a technical field to whichthe present disclosure belongs may easily implement an technical idea ofthe present disclosure. In describing the present disclosure, when it isdetermined that a specific description of a known element related to thepresent disclosure may unnecessarily obscure a gist of the presentdisclosure, detailed descriptions thereof may be omitted. Hereinafter,preferred embodiments of the present disclosure will be described indetail with reference to the accompanying drawings. In the drawings, thesame reference numerals are used to indicate the same or similarcomponents.

Hereinafter, an energy storage system according to an embodiment of thepresent disclosure will be described with reference to FIG. 2 and FIG.3.

FIG. 2 is a schematic diagram illustrating an energy storage systemaccording to an embodiment of the present disclosure. FIG. 3 is aschematic diagram illustrating a power flow according to batterycharging and discharging in FIG. 2.

First, referring to FIG. 2, an energy storage system 1 according to anembodiment of the present disclosure may manage power of a power system10, and a DC power distribution network 20 (i.e., DC power system)connected to the power system 10.

For reference, reference numerals shown in FIG. 2 and FIG. 3 are onlyapplied to FIG. 2 and FIG. 3.

Specifically, the energy storage system 1 according to an embodiment ofthe present disclosure may include a first converter 100, a battery 180,a second converter 200, a load 230, and a third converter 250.

For reference, the energy storage system may further include the powersystem 10 and the DC power distribution network 20 as well as adistributed power system (not shown) and an emergency generator (notshown). The energy storage system may further include an additionalload, for example, a DC load or an AC load other than the load 230.

In this connection, the power system 10 may include, for example, powerplants, substations, transmission lines, etc. The load 230 may include,for example, a house, a large building, and a factory. Further, thedistributed power system is configured to generate power using an energysource, and may generate power using one or more of fossil fuel, nuclearfuel, renewable energy (solar power, wind power, and tidal power). Theemergency generator, for example, may include a diesel generator and maybe connected to and disposed between the power system 10 and the firstconverter 100. When a problem occurs in the power system 10, forexample, in an event of power outage of the power system 10, theemergency generator may serve to supply the power to the load 230.

However, for convenience of illustration, an example in which the energystorage system 1 includes the first converter 100, the battery 180, thesecond converter 200, the load 230, and the third converter 250 will bedescribed herein.

The first converter 100 is connected to and disposed between the powersystem 10 and the DC power distribution network 20 to control voltage ofthe DC power distribution network 20.

Specifically, the first converter 100 may convert AC voltage suppliedfrom the power system 10 to DC voltage and may supply the DC voltage tothe DC power distribution network 20 or may convert DC voltage suppliedfrom the DC power distribution network 20 to AC voltage and may supplythe AC voltage to the power system 10.

Accordingly, the first converter 100 may act as an AC to DC converter.

Further, when the power system 10 is in a normal operation state, thefirst converter 100 may operate in a DC voltage control mode to controlthe voltage of the DC power distribution network 20.

For reference, when an accident occurs in the power system 10, that is,when the power system 10 has power outage or is disconnected, the firstconverter 100 may turn off a gate signal to stop the operation of thesystem 10.

The second converter 200 may be connected to the DC power distributionnetwork 20 and may control voltage of the load 230.

Specifically, the second converter 200 may convert the DC voltagesupplied from the DC power distribution network 20 into an AC voltageand supply the AC voltage to the load 230. Further, the second converter200 may operate in a CVCF (constant voltage constant frequency) mode tocontrol the voltage of the load 230.

Accordingly, the second converter 200 may act as a DC to AC converter,and the load 230 may act as an AC load.

The third converter 250 may be connected to and disposed between thebattery 180 and the load 230 and may control discharge of the battery180.

Specifically, the third converter 250 may convert a DC voltage suppliedfrom the battery 180 into an AC voltage and supply the AC voltage to theload 230. Further, the third converter 250 may operate in a powercontrol mode to control the power of the battery 180.

Accordingly, the third converter 250 may act as a DC to AC converter.

The battery 180 may be connected to the DC power distribution network20, and discharge of the battery 180 may be controlled by the thirdconverter 250.

Specifically, the battery 180 may receive and be charged with the powerdelivered from the power system 10 through the first converter 100 tothe DC power distribution network 20. Further, the battery 180 mayinclude at least one battery cell. Each battery cell may include aplurality of bare cells.

Further, the discharge of the battery 180 may be controlled by the thirdconverter 250. The third converter 250 may control the dischargeoperation of the battery 180 based on a discharge command received froma higher-level controller as described later.

The load 230 may be connected to the second converter 200. The voltage(i.e., power) of the load 230 may be controlled by the second converter200.

Further, the load 230 may be, for example, an AC load.

In another example, the load 230 may be a DC load. In this case, each ofthe second converter 200 and the third converter 250 may act as a DC toDC converter. However, for convenience of illustration, an example thatthe load 230 acts as an AC load will be described herein.

For reference, although not shown in the drawings, the energy storagesystem 1 according to an embodiment of the present disclosure mayfurther include a communication unit (not shown) and the higher-levelcontroller (not shown).

The communication unit may receive information about the power system 10(for example, information about whether an accident occurs in the powersystem 10) from the first converter 100, and may receive powerconsumption information of the load 230 from the second converter 200.

Further, the communication unit may transmit the information suppliedfrom the first to third converters 100, 200 and 250 to the higher-levelcontroller (not shown) and at least one of the first to third converters100, 200 and 250, depending on a situation.

The communication unit may be implemented in a high-speed communicationmanner, for example, using CAN (Controller Area Network). Thecommunication unit may communicate with the first to third converters100, 200, and 250 and the higher-level controller in a wired or wirelessmanner.

In another example, the energy storage system 1 according to anembodiment of the present disclosure may not include the communicationunit. That is, the first to third converters 100, 200, and 250 and thehigher-level controller may directly communicate with each other withouta separate communication unit.

Further, the higher-level controller may act as, for example, a PLC(Programmable Logic Controller) or EMS (Energy Management System). Thehigher-level controller may control all sequence operations of theenergy storage system 1, and may transmit a command signal to eachcomponent to perform a corresponding operation, depending on acorresponding situation.

Next, referring to FIG. 3, a power flow according to charging anddischarging of the battery 180 will be described as follows.

Specifically, in the energy storage system 1 according to an embodimentof the present disclosure, the battery 180 may directly receive and becharged with voltage from the DC power distribution network 20.

More specifically, the AC voltage supplied from the power system 10 tothe first converter 100 may be converted to the DC voltage via the firstconverter 100. The DC voltage may be transferred to the DC powerdistribution network 20. The voltage delivered to the DC powerdistribution network 20 may be directly transferred to the battery 180not via a separate converter.

That is, unlike a conventional energy storage system, the energy storagesystem 1 according to one embodiment of the present disclosure may notinclude a converter for a battery, that is, a DC to DC converter (aconverter disposed between the DC power distribution network 20 and thebattery 180). This may improve a conversion efficiency of the powerdelivered from the DC power distribution network 20 to the battery 180and may reduce a cost due to not installing the converter for thebattery.

In one example, a power flow path according to the discharge of thebattery 180 may include two paths.

First, the voltage discharged from the battery 180 may be transferred tothe load 230 via the DC power distribution network 20 and the secondconverter 200. Second, the voltage discharged from the battery 180 maybe transferred directly to the load 230 via the third converter 250.Accordingly, when the load 230 requires a power amount greater than anormally required power amount, that is, is even in the overload state,the overload applied to each converter may be reduced because thedischarging path of the battery 180 includes the first and second pathsas described above, that is, only one discharging path is not available.

Further, when one of the second converter 200 and the third converter250 fails, the power of the battery 180 may be transferred to the load230 via the other thereof. When a problem occurs in the power system 10,the power of the battery 180 may be supplied to the load 230 in anuninterruptible manner via the second and third converters 200 and 250.Thus, reliability of the power supply to the load 230 may be improved.

Hereinafter, an energy storage system 2 according to another embodimentof the present disclosure will be described with reference to FIG. 4 andFIG. 5.

FIG. 4 is a schematic diagram illustrating an energy storage systemaccording to another embodiment of the present disclosure. FIG. 5 is aschematic diagram illustrating a power flow according to batterycharging and discharging in FIG. 4.

For reference, an energy storage system 2 according to anotherembodiment of the present disclosure is the same as the above-describedenergy storage system 1 except for some components and effects thereof.Thus, following descriptions will focus on the differences therebetween.Further, reference numerals shown in FIG. 4 and FIG. 5 are applied onlyto FIG. 4 and FIG. 5.

First, referring to FIG. 4, the energy storage system 2 may include thefirst converter 100, the battery 180, the second converter 200, the load230, the third converter 250, and a fourth converter 270.

That is, the energy storage system 2 may further include the fourthconverter 270 which is not included in the energy storage system 1 asdescribed above.

In this connection, the fourth converter 270 may be connected to anddisposed between the battery 180 and the power system 10, and maycontrol charging and discharging of the battery 180.

Specifically, the fourth converter 270 may convert AC voltage suppliedfrom the power system 10 to DC voltage and supply the DC voltage to thebattery 180 or may convert DC voltage supplied from the battery 180 toAC voltage and supply the AC voltage to the power system 10.

Accordingly, the fourth converter 270 may act as an AC to DC converter.

Further, the fourth converter 270 may communicate with theaforementioned communication unit or higher-level controller in a wiredor wireless manner. In order to control the power of the battery 180,the fourth converter 270 may operate in a power control mode.

Next, referring to FIG. 5, a power flow according to charging anddischarging of the battery 180 will be described as follows.

Specifically, in the energy storage system 2 according to anotherembodiment of the present disclosure, the power flow path according tothe charging of the battery 180 may include two paths.

That is, the battery 180 may be charged upon receiving a voltagedirectly from the DC power distribution network 20 and may be chargedupon receiving the voltage via the fourth converter 270.

In this connection, the charging path via the fourth converter 270 maybe defined as a primary charging path of the battery 180. The chargingpath via the DC power distribution network 20 may be defined as anauxiliary charging path of the battery 180. In another example, thecharging path via the fourth converter 270 may be defined as anauxiliary charging path of the battery 180. The charging path via the DCpower distribution network 20 may be defined as a primary charging pathof the battery 180.

Further, when the battery 180 needs to be further charged, the battery180 may be charged only via the fourth converter 270 so as not to imposeburden to the DC power distribution network 20.

Further, in energy storage system 2 according to another embodiment ofthe present disclosure, a power flow path according to discharge of thebattery 180 may include three paths.

Specifically, first, the voltage discharged from the battery 180 may betransferred to the load 230 via the DC power distribution network 20 andthe second converter 200. Second, the voltage discharged from thebattery 180 may be transferred to the load 230 via the third converter250. Accordingly, when the load 230 requires a power amount greater thana normally required power amount, that is, is even in the overloadstate, the overload applied to each converter may be reduced because thedischarging path of the battery 180 includes the three paths asdescribed above, that is, only one discharging path is not available.

Further, when one of the second converter 200 and the third converter250 fails, the power of the battery 180 may be transferred to the load230 via the other thereof. Further, when necessary, for example, when aproblem occurs in the power system 10, the discharged voltage may besupplied to the power system 10 by discharging the battery 180 via thefourth converter 270. In another example, the voltage discharged fromthe battery 180 under control by the fourth converter 270 may besupplied to the load 230 sequentially via the fourth converter 270, viathe first converter 100, and via the second converter 200. In addition,when there is a problem in the power system 10, the power of the battery180 may be supplied to the load 230 in an uninterruptible manner via thesecond and third converters 200 and 250. Thus, reliability of the powersupply to the load 230 may be improved.

Hereinafter, an energy storage system 3 according to still anotherembodiment of the present disclosure will be described with reference toFIG. 6 to FIG. 8.

FIG. 6 is a schematic diagram illustrating an energy storage systemaccording to still another embodiment of the present disclosure. FIG. 7and FIG. 8 are schematic diagrams illustrating a power flow according tobattery charging and discharging in FIG. 6.

For reference, the energy storage system 3 according to anotherembodiment of the present disclosure is the same as the above-describedenergy storage system 2 except for some components and effects thereof.Following descriptions will focus on the differences. Further, thereference numerals shown in FIG. 6 to FIG. 8 are only applied to FIG. 6to FIG. 8.

First, referring to FIG. 6, the energy storage system 3 may include thefirst converter 100, the battery 180, the second converter 200, the load230, the third converter 250, the fourth converter 270, an auxiliarypower system 30, and a switch 290.

That is, the energy storage system 3 may further include the auxiliarypower system 30 and the switch 290 which are not include in the energystorage system 2 as described above.

In another example, the energy storage system 3 may not include theauxiliary power system 30. In this embodiment of the present disclosure,an example in which the energy storage system 3 includes the auxiliarypower system 30 will be described herein.

The auxiliary power system 30 may be connected to the load 230.

Specifically, the auxiliary power system 30 may include, for example, apower plant, substation, transmission line, etc., and may supply powerto the load 230.

Further, the auxiliary power system 30 may operate at all times, likethe power system 10 as described above. Alternatively, the auxiliarypower system 30 may be configured to operate only in an event of anemergency, for example, when the power system 10 fails. However, in thisembodiment of the present disclosure, an example that the auxiliarypower system 30 operates only in the emergency event will be describedherein.

In one example, the switch 290 may selectively connect the fourthconverter 270 to a first node N1 between the power system 10 and thefirst converter 100 or to a second node N2 between the auxiliary powersystem 30 and the load 230.

Specifically, one end of the switch 290 may be connected to the fourthconverter 270, while the other end of the switch 290 may be selectivelyconnected to one of the first and second nodes N1 and N2. That is, theswitch 290 may be connected to the first node N1 when the power system10 is operating normally. When there is a problem in the power system10, the switch 290 may be connected to the second node N2.

For reference, the auxiliary power system 30 and the switch 290 maycommunicate with the above-mentioned communication unit or higher-levelcontroller in a wireless or wired manner.

Next, referring to FIG. 7, a power flow according to charging anddischarging of the battery 180 when the power system 10 normallyoperates will be described as follows.

Specifically, the energy storage system 3 according to still anotherembodiment of the present disclosure and the energy storage system 2 asdescribed above may have the same power flow according to the chargingand discharging of the battery 180 when the power system 10 normallyoperates.

This is because when the power system 10 normally operates, the powersystem 10 and the fourth converter 270 are connected to each other viathe switch 290.

To the contrary, referring to FIG. 8, the power flow according tocharging and discharging of the battery 180 when a problem occurs in thepower system 10 will be described as follows.

Specifically, when a problem occurs in the power system 10 while thefourth converter 270 is connected to the first node N1, the fourthconverter 270 may be connected to the second node N2 via an switchingoperation of the switch 290.

Accordingly, even when a problem occurs in the DC power distributionnetwork 20, such that the discharged power of the battery 180 is nottransferred to the load 230 via the DC power distribution network 20,the discharged power of the battery 180 may be transferred to the load230 in an uninterruptible manner via the fourth converter 270 and thethird converter 250. Thus, reliability of the power supply to the load230 may be improved.

Furthermore, when the load 230 requires a power amount greater than anormally required power amount, that is, is even in the overload state,a discharging path of the battery 180 may be divided into a first pathvia the third converter 250 and a second path via the fourth converter270, thereby reducing the overload to be applied to each converter.

As described above, in the energy storage systems 1 to 3 according tosome embodiments of the present disclosure, the charging and dischargingof the battery 180 may be efficiently performed via the variousconverters, for example, the third converter 250 and the fourthconverter 270, thereby to reduce the overload to be applied to eachconverter during the discharging operation of the battery 180. Further,the non-installation of the battery converter, that is, the DC to DCconverter may reduce a cost and improve power conversion efficiency.Furthermore, even when some converters connected to the battery 180fail, a power supply path for connecting the battery 180 and the load230 to each other may be secured via the remaining converters. Thus, thereliability of the energy storage system may be secured.

Hereinafter, the energy storage system 4 according to still yet anotherembodiment of the present disclosure will be described with reference toFIG. 9 and FIG. 10.

FIG. 9 is a schematic diagram illustrating an energy storage systemaccording to still yet another embodiment of the present disclosure.FIG. 10 is a schematic diagram illustrating a power flow according tobattery charging and discharging in FIG. 9.

For reference, the energy storage system 4 according to still yetanother embodiment of the present disclosure is the same as theabove-described energy storage system 1 except for presence or absenceof a converter for a battery (that is, a DC to DC converter) as aconverter disposed between the DC power distribution network 20 and thebattery 180. Following descriptions will focus on the differences.Further, the reference numerals shown in FIG. 9 and FIG. 10 are appliedonly to FIG. 9 and FIG. 10.

First, referring to FIG. 9, the energy storage system 4 according tostill yet another embodiment of the present disclosure may include thefirst converter 100, a second converter 150, the battery 180, a thirdconverter 200, the load 230, and a fourth converter 250.

For reference, the first converter 100, the battery 180, the thirdconverter 200, the load 230, and the fourth converter 250 included inthe energy storage system 4 in FIG. 9 are the same as the firstconverter, the battery, the second converter, the load, and the thirdconverter in FIG. 1, respectively.

However, a function and a connection relationship of the secondconverter 150 in FIG. 9 is not shown in FIG. 1. Thus, the energy storagesystem 4 in FIG. 9 will be described based on this difference.

The first converter 100 may detect occurrence of an accident in thepower system 10 and supply the detection result to the second converter150. The second converter 150 may be connected to the DC powerdistribution network 20 and may control the charging and discharging ofthe battery 180.

Specifically, the second converter 150 may convert DC voltage suppliedfrom the DC power distribution network 20 into DC voltage and supply theconverted DC voltage to the battery 180 or convert the DC voltagesupplied from the battery 180 into DC voltage and supply the convertedDC voltage to the DC power distribution network 20.

Accordingly, the second converter 150 may act as a DC to DC converter.

In this connection, converting the DC voltage to the DC voltage may meanincreasing or decreasing a level of the DC voltage.

Further, the second converter 150 may operate in a power control mode tocontrol the power of the battery 180 when the power system 10 is in anormal operation state.

Specifically, the second converter 150 may perform charging anddischarging of the battery 180 based on a SOC (state of charge) of thebattery 180 and a power demand and supply situation of the power system10 when the power system 10 is operating normally. That is, the secondconverter 150 may discharge the battery 180 at a maximum load timingwhen a power consumption of the load is maximum, or may charge thebattery 180 at a minimum load timing when the power consumption of theload is minimum, such that a peak reduction function may be performed.

On the other hand, in an event of an accident in the power system 10,the first converter 100 may be stopped and, thus, the second converter150 may control the voltage of the DC power distribution network 20.

Specifically, when an accident occurs in the power system 10, the secondconverter 150 may receive the power system accident detection resultfrom the first converter 100 or may detect a voltage change rate (thatis, a DC voltage change rate over time) of the DC power distributionnetwork 20 and may determine whether an accident has occurred in thepower system 10, based on the detection result.

Further, the second converter 150 may control the voltage of the DCpower distribution network 20 based on the detection result of the powersystem accident.

That is, in the event of the accident in the power system 10, the secondconverter 150 may control the voltage of the DC power distributionnetwork 20. Thus, the power of the battery 180 may be supplied to theload 230 without delay, that is, in an uninterruptible manner.

The battery 180 may be connected to the second converter 150. Thus, thecharging and discharging thereof may be controlled by the secondconverter 150. The discharge of the battery 180 may be controlled by thefourth converter 250.

Further, the battery 180 may be composed at least one battery cell. Eachbattery cell may include a plurality of bare cells.

For reference, although not shown in the drawings, the energy storagesystem 4 according to still yet another embodiment of the presentdisclosure may further include a communication unit (not shown) and ahigher-level controller (not shown).

The communication unit may receive information (for example, whether anaccident of the power system 10 occurs) about the power system 10 fromthe first converter 100, may receive SOC (state of charge) informationof the battery 180 or voltage change rate information of the DC powerdistribution network 20 from the second converter 150, and may receivepower consumption information of the load 230 from the third converter200.

Further, the communication unit may transmit the information suppliedfrom the first to fourth converters 100, 150, 200, and 250 to thehigher-level controller (not shown) and at least one of the first tofourth converters 100, 150, 200, and 250 depending on a situation.

The communication unit may be implemented in a high-speed communicationmanner, for example, using CAN (Controller Area Network) and maycommunicate with the first to fourth converters 100, 150, 200, and 250and the higher-level controller in a wired or wireless manner.

In another example, the energy storage system 4 according to still yetanother embodiment of the present disclosure may not include thecommunication unit. That is, the first to fourth converters 100, 150,200, and 250 and the higher-level controller may directly communicatewith each other without a separate communication unit.

Next, referring to FIG. 10, a power flow according to charging anddischarging of the battery 180 will be described as follows.

Specifically, in the energy storage system 4 according to still yetanother embodiment of the present disclosure, the battery 180 may becharged upon receiving the voltage of the DC power distribution network20 from the second converter 150. On the contrary, a power flow pathaccording to the discharge of the battery 180 may include two paths.

That is, first, the voltage discharged from the battery 180 undercontrol by the second converter 150 may be transferred to the load 230via the DC power distribution network 20. Second, the voltage dischargedfrom the battery 180 under control by the fourth converter 250 may bedirectly transferred to the load 230. Accordingly, when the load 230requires a power amount greater than a normally required power amount,that is, even in the overload state, the discharging path of the battery180 may be divided into the first path via the second converter 150 andthe second path via the fourth converter 250, thereby reducing theoverload to applied to each converter.

Further, when one of the second converter 150 and the fourth converter250 fails, the power of the battery 180 may be transferred to the load230 via the other thereof. When a problem occurs in the power system 10,the power of the battery 180 may be supplied to the load 230 in anuninterruptible manner via the second and fourth converters 150 and 250.Thus, reliability of the power supply to the load 230 may be improved.

Hereinafter, an energy storage system 5 according to still yet anotherembodiment of the present disclosure will be described with reference toFIG. 11 and FIG. 12.

FIG. 11 is a schematic diagram illustrating an energy storage systemaccording to still yet another embodiment of the present disclosure.FIG. 12 is a schematic diagram illustrating a power flow according tobattery charging and discharging in FIG. 11.

For reference, the energy storage system 5 according to still yetanother embodiment of the present disclosure is the same as theabove-described energy storage system 4 except for some components andeffects thereof. Following descriptions will focus on the differences.Further, reference numerals shown in FIG. 11 and FIG. 12 are onlyapplied to FIG. 11 and FIG. 12.

First, referring to FIG. 11, the energy storage system 5 may include thefirst converter 100, the second converter 150, the battery 180, thethird converter 200, the load 230, the fourth converter 250, and a fifthconverter 270.

That is, the energy storage system 5 may further include the fifthconverter 270 which is not included in the energy storage system 4 asdescribed above.

In this connection, the fifth converter 270 may be connected to anddisposed between the battery 180 and the power system 10, and maycontrol the charging and discharging of the battery 180.

Specifically, the fifth converter 270 may convert AC voltage suppliedfrom the power system 10 to DC voltage and supply the DC voltage to thebattery 180 or may convert DC voltage supplied from the battery 180 toAC voltage and supply the AC voltage to the power system 10.

Accordingly, the fifth converter 270 may act as an AC to DC converter.

Further, the fifth converter 270 may communicate with the aforementionedcommunication unit or higher-level controller in a wired or wirelessmanner. In order to control the power of the battery 180, the fifthconverter 270 may operate in a power control mode.

Next, referring to FIG. 12, the power flow according to charging anddischarging of the battery 180 will be described as follows.

Specifically, in the energy storage system 5 according to still yetanother embodiment of the present disclosure, a power flow pathaccording to charging of the battery 180 may include two paths.

That is, the second converter 150 may convert the voltage supplied fromthe DC power distribution network 20 to charge the battery 180. Thefifth converter 270 may convert the voltage supplied from the powersystem 10 to charge the battery 180.

In this connection, a charging path via the fifth converter 270 may bedefined as a primary charging path of the battery 180, while thecharging path via the second converter 150 may be defined as anauxiliary charging path of the battery 180. In another example, acharging path via the fifth converter 270 may be defined as an auxiliarycharging path of the battery 180, while the charging path via the secondconverter 150 may be defined as a primary charging path of the battery180.

Further, in the energy storage system 5 according to still yet anotherembodiment of the present disclosure, a power flow path according to thedischarge of the battery 180 may include three paths.

Specifically, the voltage discharged from the battery 180 under controlby the second converter 150 may be transferred to the load 230 via theDC power distribution network 20. The voltage discharged from thebattery 180 under control by the fourth converter 250 may be directlytransferred to the load 230. Accordingly, when the load 230 requires apower amount greater than a normally required power amount, that is,even in the overload state, the discharging path of the battery 180 maybe divided into a path via the second converter 150 and a path via thefourth converter 250, thereby reducing the overload to be applied toeach converter.

Further, when one of the second converter 150 and the fourth converter250 fails, the power of the battery 180 may be transferred to the load230 via the other thereof. When necessary, for example, when a problemoccurs in the power system 10, the discharged voltage may be supplied tothe power system 10 by discharging the battery 180 via the fifthconverter 270. In another example, the voltage discharged from thebattery 180 under control by the fifth converter 270 may be supplied tothe load 230 sequentially via the fifth converter 270, via the firstconverter 100, and via the third converter 200. In addition, when aproblem occurs in the power system 10, the power of the battery 180 maybe supplied to the load 230 in an uninterruptible manner via the secondand fourth converters 150 and 250. Thus, reliability of the power supplyto the load 230 may be improved.

Hereinafter, an energy storage system 6 according to still yet anotherembodiment of the present disclosure will be described with reference toFIG. 13 to FIG. 15.

FIG. 13 is a schematic diagram illustrating an energy storage systemaccording to still yet another embodiment of the present disclosure.FIG. 14 and FIG. 15 are schematic diagrams illustrating a power flowaccording to battery charging and discharging in FIG. 13.

For reference, the energy storage system 6 according to still yetanother embodiment of the present disclosure is the same as theabove-described energy storage system 5 except for some components andeffects thereof. Following descriptions will focus on the differences.Further, reference numerals shown in FIG. 13 to FIG. 15 are only appliedto FIG. 13 to FIG. 15.

First, referring to FIG. 13, the energy storage system 6 includes thefirst converter 100, the second converter 150, the battery 180, thethird converter 200, the load 230, the fourth converter 250, the fifthconverter 270, an auxiliary power system 30, and a switch 290.

That is, the energy storage system 6 may further include the auxiliarypower system 30 and the switch 290 which are not included in the energystorage system 5 as described above.

In another example, the energy storage system 6 may not include theauxiliary power system 30. However, in this embodiment of the presentdisclosure, an example that the energy storage system 6 includes theauxiliary power system 30 will be described herein.

The auxiliary power system 30 may be connected to the load 230.

Specifically, the auxiliary power system 30 may include, for example, apower plant, substation, transmission line, etc. and may supply power tothe load 230.

Further, the auxiliary power system 30 may operate at all times, likethe power system 10 as described above. Alternatively, the auxiliarypower system 30 may be configured to operate only in an event of anemergency, for example, when the power system 10 fails. However, in thisembodiment of the present disclosure, an example that the auxiliarypower system 30 operates only in the emergency event will be describedherein.

In one example, the switch 290 may selectively connect the fifthconverter 270 to a first node N1 between the power system 10 and thefirst converter 100 or a second node N2 between the auxiliary powersystem 30 and the load 230.

Specifically, one end of the switch 290 may be connected to the fifthconverter 270, while the other end of the switch 290 may be selectivelyconnected to one of the first and second nodes N1 and N2. That is, theswitch 290 may be connected to the first node N1 when the power system10 is operating normally. When there is a problem in the power system10, the switch 290 may be connected to the second node N2.

For reference, the auxiliary power system 30 and the switch 290 maycommunicate with the above-mentioned communication unit or higher-levelcontroller in a wireless or wired manner.

Next, referring to FIG. 14, a power flow according to charging anddischarging of the battery 180 when the power system 10 normallyoperates will be described as follows.

Specifically, the energy storage system 6 according to still yet anotherembodiment of the present disclosure and the above-described energystorage system 5 may have the same power flow according to the chargingand discharging of the battery 180 when the power system 10 normallyoperates.

This is because when the power system 10 normally operates, the powersystem 10 and the fifth converter 270 are connected to each other viathe switch 290.

On the contrary, referring to FIG. 15, a power flow according tocharging and discharging of the battery 180 when a problem occurs in thepower system 10 will be described as follows.

Specifically, when a problem occurs in the power system 10 while thefifth converter 270 is connected to the first node N1, the fifthconverter 270 may be connected to the second node N2 via a switchingoperation of the switch 290.

Accordingly, even when a problem occurs in the second converter 150,such that the discharged power of the battery 180 is not transferred tothe load 230 via the second converter 150, the discharged power of thebattery 180 may be transferred to the load 230 in an uninterruptiblemanner via the fifth converter 270 and the fourth converter 250. Thus,reliability of the power supply to the load 230 may be improved.

Furthermore, when the load 230 requires a power amount greater than anormally required power amount, that is, even in the overload state, thedischarging path of the battery 180 may be divided into a first path viathe fourth converter 250 and a second path via the fifth converter 270,thereby reducing the overload to applied to each converter.

As described above, in the energy storage systems 4 to 6 according tosome embodiments of the present disclosure, the charging and dischargingof the battery 180 may be efficiently performed via the variousconverters, for example, the second converter 150, the fourth converter250, and the fifth converter 270. Thus, the overload to be applied toeach converter during the discharge operation may be reduced.Furthermore, even when some converters connected to the battery 180fail, the power supply path for connecting the battery 180 and the load230 to each other may be secured via the remaining converters. Thus, thereliability of the energy storage system may be secured.

The present disclosure as described above may be subjected to varioussubstitutions, modifications, and changes within the scope of thepresent disclosure without departing from the technical spirit of thepresent disclosure by a person having ordinary knowledge in thetechnical field to which the present disclosure belongs. Thus, thedisclosure is not limited to the accompanying drawings.

What is claimed is:
 1. An energy storage system for managing power of apower system and power of a direct current (DC) power distributionnetwork connected to the power system, the energy storage systemcomprising: a first converter connected to and disposed between thepower system and the DC power distribution network and configured tocontrol voltage of the DC power distribution network; a second converterconnected to the DC power distribution network; a load connected to thesecond converter, wherein the second converter is configured to controlvoltage of the load; a battery connected to the DC power distributionnetwork; and a third converter connected to and disposed between thebattery and the load in a path separate from the DC power distributionnetwork, and configured to control discharging of the battery.
 2. Theenergy storage system of claim 1, wherein the battery discharged via thethird converter is transferred directly to the load.
 3. The energystorage system of claim 1, wherein the energy storage system furthercomprises a fourth converter connected to and disposed between thebattery and the power system, wherein the fourth converter is configuredto control charging and discharging of the battery.
 4. The energystorage system of claim 3, wherein each of the first and fourthconverters is configured to convert voltage supplied from the powersystem and to charge the battery with the converted voltage.
 5. Theenergy storage system of claim 3, wherein the battery discharged via thethird converter is transferred directly to the load, wherein the batterydischarged under control by the fourth converter is transferred to thepower system.
 6. The energy storage system of claim 3, wherein theenergy storage system further comprises: an auxiliary power systemconnected to the load; and a switch configured to selectively connectthe fourth converter to a first node between the power system and thefirst converter or to a second node between the auxiliary power systemand the load.
 7. The energy storage system of claim 6, wherein one endof the switch is connected to the fourth converter, while the other endof the switch is selectively connected to either the first node or thesecond node.
 8. The energy storage system of claim 6, wherein when thepower system fails while the fourth converter is connected to the firstnode, the fourth converter is connected to the second node via answitching operation of the switch, the battery is discharged undercontrol by the fourth converter, and the battery is discharged to theload via the second node.
 9. The energy storage system of claim 3,wherein the first converter operates in a DC voltage control mode tocontrol voltage of the DC power distribution network, wherein the secondconverter operates in a constant voltage constant frequency (CVCF) modeto control voltage of the load, wherein each of the third and fourthconverters operates in a power control mode to control power supplied bythe battery.
 10. The energy storage system of claim 3, wherein the firstconverter is configured to convert alternating current (AC) voltagesupplied from the power system to DC voltage and supply the converted DCvoltage to the DC power distribution network, or to convert DC voltagesupplied from the DC power distribution network to AC voltage and supplythe converted AC voltage to the power system, wherein the secondconverter is configured to convert DC voltage supplied from the DC powerdistribution network into AC voltage and supply the converted AC voltageto the load, wherein the third converter is configured to convert DCvoltage supplied from the battery into AC voltage and supply theconverted AC voltage to the load, wherein the fourth converter isconfigured to convert AC voltage supplied from the power system to DCvoltage and supply the converted DC voltage to the battery, or toconvert DC voltage supplied from the battery to AC voltage and supplythe converted AC voltage to the power system.
 11. An energy storagesystem for managing power of a power system and power of a directcurrent (DC) power distribution network connected to the power system,the energy storage system comprising: a first converter connected to anddisposed between the power system and the DC power distribution networkand configured to control voltage of the DC power distribution network;a second converter connected to the DC power distribution network; abattery connected to the second converter, wherein the second converteris configured to control charging and discharging of the battery; athird converter connected to the DC power distribution network; a loadconnected to the third converter, wherein the third converter isconfigured to control voltage of the load; and a fourth converterconnected to and disposed between the battery and the load in a pathseparate from the DC power distribution network, wherein the fourthconverter is configured to control discharging of the battery.
 12. Theenergy storage system of claim 11, wherein voltage discharged from thebattery under control by the second converter is transferred to the loadvia the DC power distribution network, wherein the battery dischargedvia the fourth converter is transferred directly to the load.
 13. Theenergy storage system of claim 11, wherein the energy storage systemfurther comprises a fifth converter connected to and disposed betweenthe battery and the power system, wherein the fifth converter isconfigured to control charging and discharging of the battery.
 14. Theenergy storage system of claim 13, wherein the second converter isconfigured to convert voltage supplied from the DC power distributionnetwork and to charge the battery with the converted voltage, whereinthe fifth converter is configured to convert voltage supplied from thepower system and to charge the battery with the converted voltage. 15.The energy storage system of claim 13, wherein voltage discharged fromthe battery under control by the second converter is transferred to theload via the DC power distribution network, wherein the batterydischarged via the fourth converter is transferred directly to the load,wherein the battery discharged via the fourth converter is transferreddirectly to the load.
 16. The energy storage system of claim 13, whereinthe energy storage system further comprises: an auxiliary power systemconnected to the load; and a switch configured to selectively connectthe fifth converter to a first node between the power system and thefirst converter or to a second node between the auxiliary power systemand the load.
 17. The energy storage system of claim 16, wherein one endof the switch is connected to the fifth converter, while the other endof the switch is selectively connected to either the first node or thesecond node.
 18. The energy storage system of claim 16, wherein when thepower system fails while the fifth converter is connected to the firstnode, the fifth converter is connected to the second node via answitching operation of the switch, the battery is discharged undercontrol by the fifth converter, and the battery is discharged to theload via the second node.
 19. The energy storage system of claim 13,wherein the first converter operates in a DC voltage control mode tocontrol voltage of the DC power distribution network, wherein each ofthe second converter and the fourth and fifth converters operates in apower control mode to control power supplied by the battery, wherein thethird converter operates in a constant voltage constant frequency (CVCF)mode to control voltage of the load.
 20. The energy storage system ofclaim 13, wherein the first converter is configured to convertalternating current (AC) voltage supplied from the power system to DCvoltage and supply the converted DC voltage to the DC power distributionnetwork, or to convert DC voltage supplied from the DC powerdistribution network to AC voltage and supply the converted AC voltageto the power system, wherein the second converter is configured toconvert DC voltage supplied from the DC power distribution network intoDC voltage and supply the converted DC voltage to the battery, or toconvert DC voltage supplied from the battery into DC voltage and supplythe converted DC voltage to the DC power distribution network, whereinthe third converter is configured to convert DC voltage supplied fromthe DC power distribution network into AC voltage and supply theconverted AC voltage to the load, wherein the fourth converter isconfigured to convert DC voltage supplied from the battery into ACvoltage and supply the converted AC voltage to the load, wherein thefifth converter is configured to convert AC voltage supplied from thepower system to DC voltage and supply the converted DC voltage to thebattery, or to convert DC voltage supplied from the battery to ACvoltage and supply the converted AC voltage to the power system.